How is your current spare attached? The majority of the cargo racks are designed to work with swing out bumper tire carriers. I believe there are a few that work with the stock tire carrier but are limited in size and capacity due to load limits on the tailgate.
A cheap and easy alternative would be a hitch receiver cargo carrier. Could easily put up to 3-400 lbs depending upon the size. They would kill your departure angle off-road though.
There are over-the-roof options available as well. I've seen a few small baskets that bolt to the hardtop.
Beyond that, you also have the full roof racks, but that is likely far more than you need. This is the direction I'm going. I'm going to be installing a Garvin expedition rack, which is 54"x72" and carries 300 lbs.